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dp
10-22-2007, 12:05 AM
The iron used for the gears on my Grizzly lathe seems not all that great and I need to replace for the 3rd time a 35t gear. These are mod 1, 20 PA gears but I've not seen any cutters for such a configuration. My goal was to buy some decent iron and make up a batch of replacement gears for this particular gear. I've spent nearly $100 in replacements so far.

I used several methods of deriving the pitch and they all agree over the set of gears I checked. Using DP the numbers were 25.38 to 25.45 so I used metric measure and all the tests center on mod 1 which is 25.4 DP.

With mod = 1, N+2 = OD where N = number of teeth, and OD is the outside diameter in mm. Once I started using mm to measure the gears this module number jumped right out.

So I know now where to buy quality continuous cast iron, I have the dimensions and module, but where to buy a module 1 #3 cutter?

I've also started looking at John Stevenson's gear cutting page just in case.

lazlo
10-22-2007, 12:15 AM
DP, you're in the 'States, aren't you? Do the Grizzly lathes have metric (module) quadrant gears an an imperial lathe? That's seems kinda weird :)

dp
10-22-2007, 12:25 AM
DP, you're in the 'States, aren't you? Do the Grizzly lathes have metric (module) quadrant gears an an imperial lathe? That's seems kinda weird :)

Don't know the pedigree and the manual is sparse on the topic (doesn't exist). That's how the numbers came out. Using DP of 25 and 26 did not come close to the PCD as measured on any of the gears, but 25.4 did, so it is what it is. I'd read where John Stevenson had observed that a lot of Asian lathes were showing up with change gears that were metric.

Oldguy
10-22-2007, 04:20 AM
KBC Tools has module gear cutters listed in their 2007 catalog on page 220. The part number you need is 1-202-015-6 and lists for $33.19. Here's a link to the KBC site:

http://www.kbctools.com/usa/main.cfm

Glenn

John Stevenson
10-22-2007, 04:41 AM
What about buying an off the shelf steel gear from one of the gear houses in the US like Boston ?

.

dp
10-22-2007, 03:02 PM
What about buying an off the shelf steel gear from one of the gear houses in the US like Boston ?

.

Well then I'd be a home shopper machinist :). I'd like the experience and education and some satisfaction of home building the occasional odd part like this if it can be done effectively. Even if it is a bit more expensive. At 62 the brain cells start to go to sleep if you don't jog them with new stuff from time to time.

I did a scan of several gears to high magnification to see if I could grind a single point cutter to shape and it turns out (no pun) that it's not all that hard to do with this particular module as the sides are nearly straight. An electronic optical comparator (Photoshop) shows reasonably good results. I'll try it on some plastic or aluminum to see how it goes. Single pointing iron is probably not going to work, though. Still, it's educational.

Dr. Rob
10-22-2007, 04:45 PM
I can't for the life of me understand why, but for some reasonably inexplicable reason I felt compelled to make exactly such a gear at work today.

CRS, hobbed, TIR 0.03 mm, Module 1 x 20 PA x 35t. Face width 12 mm, bore 8.0 mm, boss for workholding diameter 16.0 mm, 3 mm wide.

Drop your mailing adress in my PM box, and i'll drop it in the mail tomorrow.

I don't know why.

http://i35.photobucket.com/albums/d165/DrRob101/Gear%20Hobber%20Mill/DSC00222.jpg

lazlo
10-22-2007, 07:05 PM
Wow, that's extremely nice Dr. Rob!

lane
10-22-2007, 08:57 PM
That ain`t nice that is LUCK.

dp
10-22-2007, 09:41 PM
Here's a picture taken with the gear sitting on the glass of my scanner (wife has the camera in Barcelona) which for a scanner is not a bad image:

http://thevirtualbarandgrill.com/machinery/broken_gear.jpg

Diameter is about 37mm. Scanned at 2400 dpi then resized for the dialups.

Pretty crumbly thing.

Edit: Interesting element to this image is that the lines do not converge as would be the case with a normal camera - there's no vanishing point. This creates interesting macro possibilities.

laddy
10-23-2007, 10:52 AM
Hey,
I picked up an Atlas horizontal mill off ebay quite some time ago. When I went to use it one of the drive gears for the table feed was buggered up like the one pictured above. I made a replacement out of aluminum. It was only with the help of this board that things worked out. My first two attempts ended up with the incorrect number of teeth. You can do it!!! It was fun. Fred

dp
10-31-2007, 12:29 AM
I can't for the life of me understand why, but for some reasonably inexplicable reason I felt compelled to make exactly such a gear at work today.

CRS, hobbed, TIR 0.03 mm, Module 1 x 20 PA x 35t. Face width 12 mm, bore 8.0 mm, boss for workholding diameter 16.0 mm, 3 mm wide.

Drop your mailing adress in my PM box, and i'll drop it in the mail tomorrow.

I don't know why.

http://i35.photobucket.com/albums/d165/DrRob101/Gear%20Hobber%20Mill/DSC00222.jpg

The gear showed up in the mail yesterday and it's just gorgeous! Here's a picture of it on the right meshed with the damaged gear on the left and one of the other gears from the set:

http://TheVirtualBarAndGrill.com/machinery/newgearinmesh.jpg

This image was taken at 2400 dpi on my HP scanner. I'll bore it to size and slot it for a key and turn it to the correct thickness and drop it in place. Can't thank you enough!

I'm still in awe that a conversation like this results in a piece of steel in Sweden being formed to conversational specifications and shipped half way around the world and that it fits!

Peter N
10-31-2007, 04:05 PM
Brilliant!

Nice one Dr. Rob, you're a credit to this board.

Peter

spkrman15
10-31-2007, 10:17 PM
Dr. Rob

Nice work, and you are a class act. That was really nice of you.

Rob :)

Ken_Shea
10-31-2007, 10:37 PM
Dr. Rob,
Two thumbs up, super nice and one heck of a lot more inspiring than
the aproaching offensive "http://bbs.homeshopmachinist.net/images/icons/icon1.gif For those who want a more permanent fix than provided by Viagra and Cialis? " thread, what a waste of band width that is, and soon to be , WAS.

Looks like a perfect fit Dp.

Ken

Dr. Rob
11-01-2007, 05:14 PM
You're welcome.